Audiences for content blocks, such as broadcast media or online streamed media, including commercial advertising, are typically measured via single-source data panels consisting of individuals or households recording content exposure over time. In one typical system, panel members carry a portable pager-sized device with a microphone that listens for embedded subaudible codes or watermarks in audio of media programs and records the codes it hears, indicating that the panel member was present while the program was being shown or played. The device periodically transmits its logs to a measurement server, which aggregates logs from a plurality of the devices to determine a representative viewership for the program.
At best, panels are only statistically representative of a larger population, and may become very expensive to implement as the panel size is increased in order to reduce statistical error. Additionally, panel compliance is difficult to ensure, as members may fail to carry measurement devices or fill out logs. Finally, in many instances, panel measurement data may be ambiguous to a household, and fail to distinguish between different household members' preferences.